MESOSCALE PRECIPITATION DISCUSSION 0252
NWS WEATHER PREDICTION CENTER COLLEGE PARK MD
413 PM EDT SAT JUN 20 2015
 
AREAS AFFECTED...SOUTHERN AND EASTERN OH...WESTERN PA...WV...ERN
KY...WRN MD 
 
CONCERNING...HEAVY RAINFALL...FLASH FLOODING POSSIBLE 
 
VALID 202013Z - 210200Z
 
SUMMARY...AREAS OF HEAVY RAIN WILL CONTINUE TO SPREAD EAST THIS
AFTERNOON AND EARLY EVENING.  

DISCUSSION...A WEAK SHORTWAVE IN THE NORTHERN STREAM WAS APPARENT
ON WATER VAPOR SATELLITE IMAGERY OVER THE EASTERN GREAT LAKES. 
THIS WAS CONTINUING TO ALLOW FOR EXPANSION ON THE NORTHERN
PERIPHERY OF THE PCPN SHIELD OVER SOUTHEAST OH INTO WESTERN
PENNSYLVANIA.  CONVECTIVE ALLOWING MODELS SHOW THIS TREND
CONTINUING INTO THE EVENING WITH SOME RAFL RATES OF 1.5 TO 2
INCHES PER HOUR FROM THE HEAVIEST CELLS IN THE AREA.

FURTHER SOUTH AND EAST OVER EASTERN KENTUCKY...WEST VIRGINIA...AND
PARTS OF EASTERN VIRGINIA/PENNSYLVANIA AND WESTERN MARYLAND...THE
COMBINATION OF INSTABILITY AND PRECIPITABLE WATER VALUES ON THE
ORDER OF 1.75 TO 2.00 INCHES WERE ALREADY IN PLACE.  WITH JUST AS
MUCH MOISTURE UPSTREAM BEING DRAWN INTO THE REGION BY DEEP
SOUTHWESTERLY FLOW ALOFT...SEE LITTLE REASON TO ARGUE WITH THE
CONVECTIVE ALLOWING HI RES MODEL GUIDANCE WHICH SHOWS EFFICIENT
RAINFALL PRODUCING CELLS.  RAINFALL RATES ON THE ORDER OF 2 TO 2.5
INCHES PER HOUR SEEM REASONABLE.

EVEN THOUGH THE CELLS SHOULD BE FAIRLY PROGRESSIVE...THE CONCERN
FOR EXCESSIVE RAINFALL IS THAT SOME AREAS HAVE FFG VALUES ON THE
ORDER OF 1.5 INCHES PER 3 HOURS.  

BANN

ATTN...WFO...CTP...ILN...JKL...LWX...MRX...PBZ...RLX...RNK...

ATTN...RFC...LMRFC...MARFC...OHRFC...SERFC...

LAT...LON   40508008 40497846 39967703 39417690 38557756 
            37927946 36668058 36818286 38648364 40048210